1. Technical Field
The present invention relates to a method of operating a datagram network.
2. Related Art
In recent decades, packet networks (i.e. networks that break a message up into separate parts) have become popular since they allow an efficient sharing of network resources between different users. The Internet is an example of one species of packet network, namely datagram networks (i.e. networks in which packets include a destination address unique to that network).
In his paper, ‘IETF Multiprotocol Label Switching (MPLS) Architecture’, presented at the 1st IEEE International Conference on ATM in June 1998, Francois Le Facheur describes an MPLS network. MPLS technology is likely to be widely implemented within the so-called backbone networks of the Internet. MPLS is one form of label switched network. In such a network, a label of only local significance is used by each node in determining how to forward a packet. An advantage of a label switched network over a datagram network is that a common label can be assigned to packets belonging to different messages. Packets having similar labels are processed uniformly. That results in a reduction in the amount of processing carried out by nodes within the label-switched network.
It is possible to achieve the same benefit in situations where a group of senders send packets to a single receiver (as might happen when a MPLS network operator provides a Virtual Private Network, for example). In that case, at each node in the network where flows from different senders converge, packets are received with different labels but forwarded with the same label. All packets being sent across the VPN therefore arrive at the sender with the same label. It will be realised that this aggregation leads to the processing burden placed on nodes near the receiver being lessened.
In their paper ‘Concast: Design and Implementation of a New Network Service’ available from the Proceedings of the 7th Annual International Conference on Network Protocols (October/November 1999), Kenneth L. Calvert et al, propose a method of many-to-one communication for use in the Internet. The aim of the method is to discard copies of a packet already sent to the receiver by another sender in the group. It will be seen that, as with many-to-one communications in an MPLS network, this reduces the burden on nodes closer to the receiver.